HELLO!
The PRO-83 IS NOT a trunktracking scanner. If you want to monitor a trunked system you'll need either the PRO-97 if the system is only analog, or a PRO-96 if they have APCO-25. From what I read here, you'd need a PRO-96 because the system you're trying to listen to has analog and APCO-25. Probably law enforcement is using the digital, and fire/public works etc using analog.
BTW the pro-97 is on sale right now for $149
The PRO-83 will tune in the 800mhz band. If you can enter the frequency in, and it accepts it into a memory channel, then the radio will be able to monitor it. BUT your issue could still be the antenna. If it were me I wouldn't LET ANY RADIOSHACK SALESPERSON dictate what I wanted to buy. You should go return that telescoping piece of crap and get the properly tuned 800mhz rubber-duck antenna. Don't tell them what it's for, just walk over to where they have their scanner accessories and take it off the shelf and swap it. That antenna is WAY better than the stock antenna, and better than the telescoping antenna. Chances are the PRO-83 doesn't have as good as a receiver as the 2040. I still think getting a PRO-97 would be better since it's designed specifically for trunking.